1. Field of the Invention
The present invention relates to fan control, and, more particularly, to power management techniques for a variable speed fan.
2. Description of the Related Art
Fans are standard components in many commercial computers, workstations, notebook and desktop personal computer systems, and in many other electronic and mechanical systems. Fans remove heat generated due to operation of integrated circuits and other components in such systems. An example of a common type of fan is the brushless DC fan. Brushless fans do not include a conductor serving to maintain an electrical connection between stationary and moving parts of the fan.
The use of fans often presents certain disadvantages in various systems. For example, fans generate objectionable acoustic noise, especially when run at full speed. Also, fins often have a service life which is less than the service life of the equipment they protect. Additionally, fans require large amounts of operating current which can present a problem for low power, "green" personal computer systems.
Many systems vary the speed of the fan directly with measured temperature. For example, fan speed is increased with increases in measured temperature. Such a thermal fan speed control may be built into the fan itself or provided by supplemental circuitry such as a processor within the system. To further minimize the disadvantages of fans, a fan may operate only when required and be turned off (herein, shutdown) during all other times. However, if excessive heat is generated within the system when the fan is in shutdown, system safety is compromised. Consequently, the system should constantly monitor temperature and intervene (e.g., terminate shutdown) when cooling is required. Such capability requires additional software and/or hardware, thereby increasing system complexity. Thus, there is a need for a simple, effective and inexpensive method and/or apparatus for minimizing the above discussed disadvantages of fan use.